While the source code for the Paperscape browser-based map client was released on Github in early 2015, the back-end code first required a clean up before it could meet a similar fate. The inspiration to finally do so came from a Paperscape-related project we worked on for the Max Planck Digital Library in September this year. As a result, a significant part of the Paperscape back-end is now available on Github under a MIT license. That includes the code for n-body map generation (written in C), map tile generation (written in Go), and the web-server (also in Go).

Since the beginning of the paperscape map it’s been possible to search for daily new papers of a given arXiv category. For example, the search query ?new-papers hep-ph,crosslists searches for new papers in high energy phenomenology and papers cross-listed to this category for the most recent submission day.

What’s new is that we’ve added a popup box (accessible from the “new papers” link next to the search box) that not only makes searching for new papers easier (no need to type a query), but also more powerful! You can now ask for all newly submitted papers occurring within a specific date range, which spans back to 31 previous submission days.

For example, if you’ve haven’t had the time to check the arXiv in the last two weeks, you could ask to see all new papers from the last 10 submission days:

And then zoom in on your area of interest, the neutrino landscape for example, to quickly see what papers you have missed:

We’ve also made it easier to select search results: clicking anywhere within the highlighted white halo of a search result paper will select it. To remove the halos, simply “clear” the search result.

In other news, you may have noticed that the map looks slightly different since the beginning of this year. This is because we regenerated it from scratch in order to let some papers that had become stuck (due to the close repulsive force) move into their natural positions. It’s also worth noting that paperscape now includes the entire author list for all papers, i.e. papers with a very large number of co-authors are now searchable (identified with) each one of these authors.

This week we were contacted by Roberto Salazar, who has recently completed a PhD at the University of Concepción in Chile on quantum information. He told us he was inspired by the Paperscape map, and that he had set out to create a personal characterization of the quantum mechanics continent:

The quantum mechanics continent in the Paperscape map

To that end he teamed up with digital designer Sebastián Pizarro , and together they came up with “Quantum Earth”:

It’s now possible to view all the references or citations of a paper that appear in the map. To do so, simply click on the appropriate link at the bottom left of the info box. These links along with the star-like result can be seen in this example screenshot:

View references or citations of a paper in the map.

Note that by references we mean the papers a given paper refers to in its bibliography, and by citations we mean the papers that refer to (cite) it.

The viewing of references/citations is implemented as a search result, so the links in the selected paper’s info box are just shortcuts for the appropriate search. That means you can also search for the references or citations of an arXiv ID directly using ?refs <arXivId> or ?cites <arXivId>, respectively. For example, to search for the references of hep-th/9711200 you could enter the search query: ?refs hep-th/9711200

Our original colouring scheme for the generated Paperscape map assigns the arXiv categories (mostly) unique colours to easily distinguish them. This colour coding shows clearly how authors cite mostly within their own fields, as well as revealing interesting interfaces between the different categories. For example, check out the fields of dark matter (astrophysics meets high energy phenomenology) and dark energy (high energy theory meets general relativity/quantum cosmology meets astrophysics). However, the cost of using colour to code categories is that other features, such as a paper’s age, must be shown in a different way. Specifically, we use brightness to highlight newer papers in this scheme, but, due to all the different colours present, new regions of papers don’t really shine through.

Enter our new heatmap, which purely shows the age of papers using a colour gradient from dark gray (old) to bright red (new). The heatmap can be activated using the new drop down menu located at the top left of the map. In this new colouring scheme regions of recent activity stand out much more clearly, and new papers that are growing quickly can be easily identified. If you haven’t yet, go visit the Paperscape map to try it.

Comparison of category and heatmap colour schemes

Now for some details. We found that a linear mapping of the arXiv’s paper ages (spanning 23 years) to the chosen colour gradient wasn’t sufficient to highlight recent activity. After trying various mappings, we’ve opted for a Voigt profile with a sigma of 4 years and a gamma of 1/27 inverse years. These values simply represent what we think best distinguishes what’s currently hot with what’s not. We’ll probably continue to tune the heatmap in the future, and your suggestions are very welcome!

By giving the map two different colour schemes, the question of whether there are other interesting colour schemes naturally arises. It could for example be useful to highlight trending papers i.e. papers that are growing quickly in their number of citations, irrespective of their age. If you have any good ideas please share them!